Yaskawa GA700 output reactor
Size by drive current and voltage when long motor leads are causing capacitive overcurrent trips.
$80-$320
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Yaskawa GA700 OC Fault — What It Means
The Yaskawa GA700 is the latest generation general-purpose inverter, succeeding the A1000 series. The OC fault (Overcurrent) appears when the drive’s output current exceeds 200% of the drive’s rated current. The GA700 has enhanced current detection compared to earlier Yaskawa drives and can distinguish between acceleration overcurrent (oC1), deceleration overcurrent (oC2), and constant-speed overcurrent (oC3), giving you a more precise indication of when in the operating cycle the fault occurs.
OC Sub-Faults on the GA700
| Code | When It Occurs |
|---|---|
| oC1 | During acceleration |
| oC2 | During deceleration |
| oC3 | At constant speed |
Common Causes
- oC1 (During acceleration) — Acceleration time too short for the load inertia, mechanical obstruction (seized bearing, jammed conveyor), or a winding-to-winding short in the motor. Extend the acceleration ramp (parameter C1-01) and verify the load is unobstructed.
- oC2 (During deceleration) — Deceleration time too short for a high-inertia load. The motor is being regenerated too aggressively and the current spikes. Extend the deceleration time (parameter C1-02) or add a dynamic braking resistor/unit.
- oC3 (At constant speed) — A sudden mechanical overload: a pump running against a closed valve, a conveyor carrying a jammed object, a fan blade striking debris. Also caused by motor winding damage or a ground fault.
- Motor cable too long — Long motor cables (over 100 feet) create capacitive charging currents that the drive reads as overcurrent. This is more common on the GA700’s high-frequency carrier (default 2 kHz).
- Incorrect motor parameters — If the motor nameplate data entered in the GA700’s parameter groups (E1-02 through E1-09 for motor ratings) doesn’t match the actual motor, the drive’s overcurrent protection may trigger at the wrong level.
Step-by-Step Fix
- Note the exact sub-fault code (oC1, oC2, or oC3) — The sub-fault tells you when in the cycle the overcurrent occurs, which directs you to the right fix.
- For oC1 — Increase the acceleration time in parameter C1-01. Start by doubling the current value. Also verify the load is freely rotating by hand (with power off) before restarting.
- For oC2 — Increase the deceleration time in parameter C1-02. If the load has very high inertia (large fans, centrifuges), add a dynamic braking unit and resistor to absorb regenerative energy.
- For oC3 — Check the mechanical load. Remove the obstruction if present. Measure motor phase currents with a clamp meter during steady-state operation — they should be balanced and below nameplate FLA.
- Megger the motor — With the motor disconnected from the drive and power off, test insulation resistance phase-to-ground (500V DC megger). Values below 1 MΩ indicate deteriorating insulation that will produce intermittent OC faults.
- Check motor cable length and shielding — If the cable run exceeds 100 feet, add a load reactor (output choke) at the drive output terminals to reduce capacitive charging current.
- Verify motor parameters — Navigate to the GA700’s E1 parameter group and confirm motor voltage (E1-01), motor rated current (E1-03), motor rated frequency (E1-04), and motor rated speed (E1-05) all match the motor nameplate.
- Run auto-tune — After confirming motor parameters, run the GA700’s auto-tune function (T1-00 parameter). Auto-tune measures the actual motor characteristics and optimizes the drive’s control performance, which can eliminate OC faults caused by improper vector control tuning.
Parts Often Needed
| Part | Notes |
|---|---|
| Output reactor (load reactor) | For long cable runs >100 ft; reduces capacitive OC faults |
| Dynamic braking resistor/unit | For oC2 on high-inertia loads |
| Motor (replacement) | If megger test shows insulation breakdown |
Technician Tips
When diagnosing VFD faults, always check the drive’s fault history before resetting. Modern drives store the last 5-10 faults with the drive state at the time (running, accelerating, decelerating, stopped). An overcurrent fault that occurs only during acceleration points to incorrect motor data or mechanical binding. The same fault during deceleration suggests regeneration issues. A ground fault that clears after disconnecting the motor and returns when reconnected means the motor or cable insulation has failed.
Prevention: Schedule annual infrared scanning of drive cabinets. Loose power connections and failing capacitors produce heat long before they cause faults. A 5-minute scan can prevent hours of unplanned downtime.
Need Replacement Parts?
Before ordering, match the drive part to the model number, voltage class, amp rating, motor lead length, and confirmed OC sub-fault. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If oC3 persists with a confirmed healthy motor, correct cable length, and properly tuned drive parameters, the GA700’s IGBT output stage may have developed a fault. Yaskawa’s Technical Support Center (1-800-927-5292) can walk through advanced diagnostics, or the drive can be sent to a Yaskawa authorized repair center for board-level testing.